Metal maps not only give us constraints on the effects of AGN feedback, but can also constrain different AGN feeding modes. Fig. REF  shows two HR HD simulations testing two different models of AGN self-regulation and feeding in a massive galaxy group with extended IGrM (\(L_{\rm x}\sim 10^{43}\,{\rm erg\,s^{-1}}\) ).
In the left panel, CCA feeding/cold mode self-regulation drives a very intermittent duty cycle tightly related to the recent cooling rate in the group core (typically with pink-noise time power spectrum; [1]}). The rapid flickering of the AGN enables the formation of characteristic AGN feedback imprints, such as buoyant bubbles and cocoon shocks that are encased by metal-rich rims (cyan) protruding on top of the low abundance background. In addition, the buoyant bubble can dredge out trailing filaments of metals via the hydrodynamical [2]} effect (\(V_{\rm trail} \sim 0.5\,V_{\rm b}\) , where \(V_{\rm b}\)  is the bubble volume).
Conversely, hot-mode feeding (e.g., Bondi or ADAF; [3]}, [4]}) drives a continuous AGN feedback evolution with a perennial, monolithic, wide and uniform cylinder of metals, without any signs of cavities or shocks. As for the thermodynamics [5]}, observational constraints favor the former intermittent bubble duty cycle (via cold mode/CCA), rather than the latter quasi-continuous triggering mode (Bondi or hot-mode feeding) – [6]}, [7]}, [8]}, [9]}, [10]}, [11]}.
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